areole

Areoles are the distinctive feature of cacti, and identify them as a separate family from other succulent plants. Areoles give rise to spines or, on certain cacti, small, detachable glochids which are an additional form of protection. The areoles on cacti are clearly visible. They generally appear as small light to dark colored bumps, out of which grow clusters of spines.
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n. areola, halo

n. areola, dark band of skin which surrounds a nipple; very small area; plant cell

(n.)
Same as Areola.
  

AREOLA